Effort-Reduced Calibration of Six-Port Based Receivers for CR/SDR Applications

Abstract

This paper presents an effort-reduced approach for calibrating the reconfigurable six-port based receiver (SPR) systems for cognitive radio/software defined radio applications that accounts for all the known imperfections and impairments of an SPR system. The state-of-the-art calibration method requires estimation of more than 100 calibration parameters on-the-fly. The proposed calibration method reduces the number of parameters to four without any sacrifice in the overall system performance. The proposed method uses a different structure for six-port junction to ease the calibration effort. The nonlinearity and the frequency response of the system are broken down into two different realms. Nonlinearity of the system is accounted for by continuous wave characterization of the diode detectors while the frequency response is compensated for using an equalizer in the calibration step. The results obtained for the proposed approach are compared with the state-of-the-art calibration method. Similar performance from the SPR system is obtained with much reduced calibration complexity.Index Terms-Calibration, cognitive radio (CR), diode linearization, direct conversion receiver, memory effect, multiport, software-defined radio (SDR).